Lightweight polymer concrete composition

ABSTRACT

A lightweight foamed polymer concrete admixture for use in fabricating building components, the polymer concrete comprising a mixture of a polyol, an isocyanate, an aggregate, and water, wherein once mixed, the mixture releases carbon dioxide gas creating a foamed mixture that may be shaped to form a building component such as, but not limited to, lap siding, shake siding, trim boards, stone and stucco sheeting.

RELATED APPLICATION

This application claims the benefit of priority to U.S. ProvisionalApplication No. 61/805,551 filed on Mar. 26, 2013 and is a continuationof U.S. application Ser. No. 14/226,495 filed on Mar. 26, 2014.

TECHNICAL FIELD

This invention relates generally to the formation of decorative andstructural building components made from a polymeric concrete admixture.

SUMMARY

Consumers are increasingly demanding that exterior building componentssuch as lap siding, roof shakes, siding shakes, bricks, paving stones,stucco sheeting and lap siding provide a high quality appearance and yetare also extremely durable. These components are built to exactingspecifications and constructed of materials that are capable ofwithstanding the bleaching effects of high intensity sunlight, daytimesurface temperatures in excess of 250° F., repeated exposure to strongwinds, hail impact, sub-zero temperatures and the typical insultsbuilding materials are exposed to throughout the United States includingimpacts from errant baseballs, hockey pucks, soccer balls, abrasive treelimbs and the like. In other words, the typical building component mustnow be nearly indestructible in order to maintain customer loyalty.

The building products must be hard, yet ductile and not brittle, towithstand high energy impacts and also impacts from tools, such ashammers, during installation. The building materials must have hightensile and compressive strengths to avoid undesirable deformation underloads or fracture when nails or screws are driven through the product.In addition, the building components must have low thermal expansion toavoid buckling when temperatures vary during a short time period such asat sunset in desert settings. The building components must be capable ofretarding fires, have low moisture absorption and preferably addsR-value to provide insulating qualities thereby lowering energy costsfor the consumer.

Making these building components capable of withstanding high energyimpacts, temperature extremes and wind loading is a challenging taskthat requires considerable expertise with material properties. Furthercomplicating the task of fabricating these building components is thechallenge of producing components that are lightweight so that theindividual installing the building component (e.g., siding) is notinjured while attempting to move, for example a heavy panel, orprematurely experiences muscle fatigue from repeated movement of smalleryet heavy components such as siding shakes.

In order to integrate the many desirable characteristics referencedabove the disclosed technology utilizes a polymer concrete admixturethat invokes a polymerization reaction with water to intentionally causethe release of carbon dioxide gas. The release of the carbon dioxide gasfoams the admixture by introducing the gas bubbles into the polymerconcrete mixture. This foaming activity causes entrainment of the gaswithin the admixture thereby causing a set volume of the material withentrained carbon dioxide gas to weigh less, per unit of volume, than theadmixture without the entrained carbon dioxide gas. The material withthe entrained carbon dioxide gas weighs roughly one-half of what thenon-entrained gas mixture weighs by a set volume of the material. Whenthe gas entrained polymer concrete is molded into the desired product itmaintains excellent structural strength, fire retardance, a low thermalexpansion coefficient and many other desirable characteristics and alsoweighs substantially less than a product that did not undergo thefoaming process.

For the foregoing reasons, there is a need for a polymer concreteadmixture that can be shaped to form exterior weatherable buildingproducts.

For the foregoing reasons, there is a need for a polymer concreteadmixture that has a low specific gravity in order that finishedproducts are of the lightest weight possible without sacrificing otherdesirable performance characteristics.

For the foregoing reasons, there is a need for a polymer concreteadmixture that has low moisture absorption.

For the foregoing reasons, there is a need for a polymer concreteadmixture that has a low coefficient of thermal expansion.

For the foregoing reasons, there is a need for a polymer concreteadmixture that is fire retardant.

For the foregoing reasons, there is a need for a polymer concreteadmixture that adds R-value thereby enhancing the energy efficiency ofthe structure to which the building product is applied.

SUMMARY

The disclosed technology is directed to a multiplicity of buildingproducts that satisfies the requirements of high strength, high impactresistance, a low coefficient of thermal expansion, adds R-value, lowmoisture absorption, is fully resistant to wood rot, decay and insectsamong other important characteristics by using a light weight foamedpolymer concrete that is molded into the desired shape. The polymerconcrete that is employed is comprised of a mixture of a polyol, anisocyanate, an aggregate and water, wherein once mixed, the admixture isshaped to form the desired building component.

Exemplary building products that are produced using the disclosedtechnology include, but are not limited to lap siding, shake sidingpanels, shake roofing, paving stones and decking materials as well asexterior stucco sheeting and trim boards. Once the above referencedmaterials are combined and thoroughly aggregated the admixture ismolded, extruded or pultruded to form the desired shape. Because of therelease of carbon dioxide gas the admixture upon the addition of waterbegins to release carbon dioxide and form a foamed product. The foamedproduct has a density of approximately one-half that of the sameadmixture that does not have water introduced into the mixture.

The low density of the fully cured foamed product is a central attributeof this composition and system for production of building products. Withbuilding product densities ranging from 0.7 to 1.5 g/cm³ the productproduced from the disclosed implementation is lightweight in comparisonto standard concrete. Industrial concrete typically has a density ofabout 2.4 g/cm³ and therefore a paving stone produced from the disclosedcomposition may weigh only one-third that produced from standardindustrial concrete. Weight savings of this magnitude will quicklytranslate into savings in shipping costs as well as fewer workplace softtissue and joint injuries due to excessive weight being borne by theinstaller when moving the building products.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the method for admixing the polymer concretecomposition;

FIG. 2 is a perspective view of an embodiment of lap siding fabricatedfrom the polymer concrete composition;

FIG. 3 is a perspective view of an embodiment of roof shakes fabricatedfrom the polymer concrete composition;

FIG. 4 is a perspective view of an embodiment of siding shakesfabricated from the polymer concrete composition;

FIG. 5 is a perspective view of an embodiment of siding stonesfabricated from the polymer concrete composition;

FIG. 6 is a perspective view of an embodiment of paving stonesfabricated from the polymer concrete composition, and

FIG. 7 is a perspective view of an embodiment of stucco sidingfabricated from the polymer concrete composition.

DETAILED DESCRIPTION

The invention may be more fully appreciated by reference to thefollowing detailed description, including the following glossary ofterms and the example.

The terms “including”, “containing” and “comprising” are used herein intheir open, non-limiting sense.

“Admixture” means the ingredients in the polymer concrete that are addedto the mix immediately before or during mixing.

“Cure” means the process of toughening or hardening of a polymermaterial by cross-linking of polymer chains, brought about by chemicaladditives, ultraviolet radiation or heat.

“Polymer concrete” means the group of concretes that use polymers toreplace cement as a binder.

The following detailed description is directed to a method of producingbuilding materials from a polymer concrete mixture that possess highlydesirable physical characteristics and that can be shaped into a widevariety of products for consumer use. Building materials such as siding,shakes, and trim boards must possess a wide range of physicalcharacteristics that facilitate their continued use in the constructionindustry. Specifically, the building materials must have high tensileand compressive strengths yet be sufficiently ductile to avoid brittlefacture particularly at low temperatures, they must be flame retardant,have a low coefficient of thermal expansion and contributes R-value toreduce the transfer of heat. Moreover, the material selected for thebuilding products must be easily and quickly formed into the desiredshape and finally must be lightweight to reduce shipping costs and toenhance the ease of installation.

In the following detailed description, references are made to theaccompanying drawings that form a part hereof, and that show by way ofillustration specific embodiments or examples. Referring now to thedrawings, in which like numerals represent like elements through theseveral figures, the process of producing building materials from apolymer concrete mixture will be described.

FIG. 1 shows a flow diagram depicting the sequence of the aggregation ofa series of materials to form the polymer concrete admixture 10. Block 1depicts the selection of polymeric polyol 20 which is an alcoholcontaining multiple hydroxyl groups. The selected polymeric polyol maybe either derived from vegetable sources, such as corn, or the polyolmay be petroleum based. The preferred embodiment utilizes a vegetablebased polyol for use in the polymer concrete admixture. The polyol 20will preferably comprise in the range of 10 to 15% of the mass of thetotal mixture.

Block 2 of FIG. 1 reveals the selection of an isocyanate 30. Thepreferred isocyanate is the aromatic isocyanate diphenylmethanediisocyanate, commonly referred to as MDI. Alternatively, the aromaticisocyanate toluene diisocyanate, commonly referred to as TDI, may beused. The isocyanate will preferably comprise in the range of 5 to 15%of the total mixture.

A third component for inclusion in the mixture, as seen in block 3, isan aggregate 40. The preferred aggregate is sand with an averageparticle size in the range of about 10 to 1,000 microns. Alternativessuch as quartz silica, calcium carbonate or talc and other minerals mayalso be utilized in place of the sand. The aggregate 40 will serve asthe backbone of the admixture and serve to provide structural rigidityto the composition when cured and also enhance the composition'sweatherability, fire retardance, low thermal expansion characteristicsand high R-value. The aggregate preferably comprises between about 50%to 90% of the mass of the total mixture. The aggregate furtherpreferably comprises about 80% of the mass of the admixture.

The fourth component of the composition, as seen in block 4, is water50. Water will comprise a very small percentage of the overall mass ofthe admixture but generally no less than 0.1% of the total mass of themixture. Any water that does not react with the available isocyanate 30is flashed off later in the molding process. The isocyanate 30 reacts inthe presence of water 50 to form a urea linkage and carbon dioxide gas60. The carbon dioxide gas forms throughout the admixture and createstiny entrained bubbles of gas in the mixture.

The fifth component that may be added to the admixture, as seen in block5, is a catalyst 70. At least two forms of catalyst may be used to alterthe rate of the reaction of the constituents of the admixture. These twoforms of catalyst are an amine compound catalyst and a metal compoundcatalyst. The catalyst does not serve to alter the characteristics ofthe admixture when fully cured, it does, however, serve to change therate at which the mixture cures and is ready for release from the moldinto which it is placed for shaping into a finished product.

The sixth component that may be added to the admixture is fiber. Theintroduction of fiber serves to increase the flexural and strengthmodulus as well as abrasion and impact resistance, to reduce theincidence of crack propagation. The preferred forms of fiber added tothe admixture are chopped glass about one-quarter inch in length, milledglass, preferably one-sixteenth inch in length, cellulosic fibersprincipally cotton fibers, preferably about 4 mm in length. Fiber ispreferably added in the amount ranging from 1 to 5% by weight of thetotal admixture. A range of fiber mass from 2 to 3% is furtherpreferable.

To produce the desired mixture 10 the isocyanate 30 is blended with thepolymeric polyol 20. The preferred ratio for blending this portion ofthe admixture is one part isocyanate 30 to one part alcohol content inthe polymeric polyol 20. Consequently, more polymeric polyol 20, bymass, is added to the mixture as compared to isocyanate 30. Once thesematerials 20, 30 are blended the composition begins react. At this timethe aggregate 40, preferably sand with a mean diameter in the range offrom 10 to 1,000 microns, is added to the mixture. The aggregate 40comprises preferably in the range of 50% to 90% by total mass with afurther preference for the aggregate to provide roughly 80% of the totalmass of the polymer concrete admixture.

As discussed above, the isocyanate 30 reacts with water to form carbondioxide gas. Many times the aggregate, unless thoroughly dried willcontain sufficient moisture (water 50) for reaction with the isocyanate30. If a greater release of carbon dioxide gas for entrainment withinthe admixture is desired, additional water is added. Excess water;however, will flash-off during the molding process. As previouslydiscussed, the mass of water added to the admixture is preferably inexcess of 0.10% but less than 2%.

Once the admixture containing the polymeric polyol 20, the isocyanate30, the aggregate 40 and the water 50 is thoroughly blended so that thematerial is essentially homogenous throughout the admixture 10 is placedinto a closed mold 80 of the shape desired for the building product.

Alternatively, double-belt presses with circulating belts make itpossible to implement continuous production processes (not shown).Continuous production methods can increase production capacity whileachieving lower energy consumption. Pressing, heating and cooling themixture, to produce for example siding panels, is achieved in a singleproduction step. Siding panels can be manufactured with increasedprecision within tight tolerances for specified density.

The admixture 10 will continue to expand due to the entrainment of thecarbon dioxide gas 60 to fill the volume of the closed mold 80.

In an exemplary scenario that is not intended to limit the range ofalternatives available in the curing and demolding process, theadmixture is then cured in the mold for approximately 2 hours at 100° C.and then demolded. Upon demolding, the product is post cured forapproximately 16 hours at 70° C. Products that are not fully cured atelevated temperatures for the requisite period of time will suffer fromdeficiencies in the desired physical properties including reducedtensile strength, glass transition temperature and flexural strength andmodulus. The increased temperature in the mold serves as a catalyst toaccelerate the polyurethane linkage.

To further enhance the aesthetic appeal of the finished productscoloration can be accomplished with the addition of pigments to theadmixture during the mixing process. To further enhance the durabilityand weatherability of the finished materials certain building productsproduced from the disclosed composition, such as lap siding and shakes,may also include a protective fully encompassing cap that is preferablycomprised of polyvinyl chloride (PVC) or acrylonitrile styrene acrylate(ASA). The cap is preferably in the range of 3 to 5 mils in thicknesswhen applied using methods that are well known to those skilled in themanufacture of capped composite building materials. Paint and filmscomprised of acrylic preferably about 0.001 inches in thickness are alsooptions available to protect the finished product.

As seen in FIGS. 2-7, a wide range of products 90 (lap siding), 100(roof shakes), 110 (shake siding), 120 (brick), 130 (stone pavers) and140 (stucco) can be produced from the polymer concrete admixture 10.

EXAMPLE

The invention is described in greater detail below by means of anexemplary embodiment, the physical property determination methodsdescribed herein are being used for the corresponding parameter in theimplementation unless otherwise indicated.

Materials:

For the production of test specimens, the polyol BiOH X-210® produced byCargill with an OH of 225, an acid value of 11.4 and an equivalentweight of 249 is used. The mass percentage of the polyol was 12.3% ofthe total mixture.

Isocyanate Rubinate® M from Huntsmen Chemical with an NCO % of 31.2 afunction number (FN) of 2.7 and an equivalent weight (EW) of 135 isused. The mass percentage of the isocyanate is 9.0% of the totalmixture.

The aggregate Sea Sand from Fisher Scientific comprised of quartz silicawith a density of 2.65 g/cm³ and an average particle size of 300 micronsis used. The mass percentage of the aggregate is 78.2% of the totalmixture.

Distilled water equivalent to 0.50% of the overall mass is utilized.

Compounding:

Compounding of the above referenced additives is carried out in a sixquart stand mixer manufactured by Kitchenaid®.

Test Specimens:

The compounded material is withdrawn from the stand mixer and placedinto a mold for producing plank siding. The dimensions of the mold are24″×8″× 5/16.″ The samples are cured for 16 hours at 120° C.

Measurement of Physical Parameters:

The specimens are tested to determine physical parameters, many of whichare standard test protocols defined by American Society for Testing andMaterials (ASTM International). The specific testing protocols are setforth below in Table 1.

TABLE 1 Physical Parameter ASTM or other Test Method Identifier TensileStrength ASTM D638 Tensile Elongation ASTM D638 Tensile Modulus ASTMD638 Density ASTM D1622 Flexural Strength ASTM C293 Flexural ModulusASTM C293 Gardner Impact Falling Dart Impact Glass Transition DynamicMechanical Analysis (DMA) Temperature—Tg Coefficient of Expansion—COEThermal Mechanical Analysis (TMA)

Example 1

The results of the physical parameter measurements are given in Table 2.

TABLE 2 PROPERTY UNITS VALUE Tensile Strength Mpa  9.0-37.0 TensileElongation % 0.8-1.7 Tensile Modulus Mpa 2810-4650 Density g/cm³ 0.9-1.13 Flexural Strength Mpa 6.0-9.0 Flexural Modulus Mpa 380-560Gardner Impact Kg * cm 25-50 Tg (glass transition ° C.  80-146temperature) COE (coefficient of thermal μm/m ° C. @ 25° C. 10.2-40.6expansion)

While the preferred form of the present invention has been shown anddescribed above, it should be apparent to those skilled in the art thatthe subject invention is not limited by the figures and that the scopeof the invention includes modifications, variations and equivalentswhich fall within the scope of the attached claims. Moreover, it shouldbe understood that the individual components of the invention includeequivalent embodiments without departing from the spirit of thisinvention.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations and are contemplated within the scope of the claims. Notall steps listed in the various figures need be carried out in thespecific order described.

We claim:
 1. A polymer concrete composition useful for fabricatinglightweight building products, the polymer concrete compositioncomprising; (a) aggregate in an amount in the range from about 50 to 90%by weight of the polymer concrete composition; (b) polyol in an amountin the range from about 10 to 20% by weight of the polymer concretecomposition; (c) isocyanate in an amount in the range from about 5 to15% by weight of the polymer concrete composition; and (d) water in anamount of at least 0.1% by weight of the polymer concrete composition,wherein the sum of the components (a) through (d) add up to 100 weight %and after the product is cured in a continuous belt mold the polymerconcrete exhibits a density of from about 0.7 to 1.5 g/cm³ and aflexural strength of from about 0.6 to 1.0 Mpa.
 2. The polymer concretecomposition of claim 1, wherein fibers are added to the admixture in therange of about 1 to 5%.
 3. The polymer concrete composition of claim 2,wherein chopped glass fibers preferably about one-quarter inch in lengthare added to the admixture.
 4. The polymer concrete composition of claim2, wherein milled glass fibers preferably about one-sixteenth inch inlength are added to the admixture.
 5. The polymer concrete compositionof claim 2, wherein cellulose fibers are added to the admixture.
 6. Thepolymer concrete composition of claim 2, wherein cotton fiberspreferably about 4 mm in length are added to the admixture.
 7. Thepolymer concrete composition of claim 1, wherein the cured buildingproduct is covered with a cap comprised of polyvinyl chloride in athickness ranging from about 0.003 to 0.005 inches.
 8. The polymerconcrete composition of claim 1, wherein the cured building product iscovered with a cap comprised of acrylonitrile styrene acrylate in athickness ranging from about 0.003 to 0.005 inches.
 9. The polymerconcrete composition of claim 1, wherein the composition is cured in amold for 2 hours at 100° C. and then demolded and cured for at least 2hours at a temperature between 60 and 120° C.